1: Eur J Pharm Sci 1998 Oct 1;6(4):311-316
Evaluation of the formalin test to assess the analgesic activity of diflunisal
in the rat.
Meunier CJ, Burton J, Cumps J, Verbeeck RK
Laboratories of Pharmacokinetics and Medicinal Chemistry, School of Pharmacy,
Catholic University of Louvain (UCL), 1200 Brussels, Belgium
[Record supplied by publisher]
The formalin test was evaluated to assess the analgesic activity of diflunisal
in the rat. Fifty microliters of a 5% formalin solution was injected into
the hindpaw of rats and two distinct nociceptive behaviors, i.e. flinching/shaking
and licking/biting of the injected paw, were recorded over 120 min. The
effect of factors such as age of the animal, time of injection (morning
vs. afternoon), site of injection (right vs. left hind paw) were evaluated.
Both nociceptive behaviors exhibited a biphasic time course. Rats weighing
210-220 grams showed a more intense response compared to older rats weighing
240-250 or 270-280 grams. The nociceptive behavior response was affected
by the time of formalin injection and was more pronounced in the morning.
Diflunisal (100 mg/kg, i.v. infusion over 3 min) caused a significant delay
in the flinching/shaking response vs. time curve, whereas the licking/biting
response was significantly inhibited. When carried out under carefully
controlled conditions, the formalin test may be useful to study the analgesic
effect of diflunisal in the rat. It seems to be less sensitive, however,
than other commonly used nociceptive tests.
PMID: 9795087